Osama Bin Laden has claimed that Al-Qaeda was solely responsible for
the 9/11 attacks. The US Governments investigations into the events
of 9/11 also came to the conclusion that Al-Qaeda was solely responsible.
Bin Laden has since claimed in a radio broadcast that the reason for
the attack was part of the, "fight, Allah willing, against the
Isreali's and their allies, in order to pursue justice for the oppressed."
This places the events of 9/11 as being the culmination of a long power
struggle in the Middle East, which has its origins hundreds of years
previously. Below is a brief timeline of events that have demonstrated
an escalation in anti-western / US extremism from radical muslim groups.
For longer term conflicts between muslim extremists and the west, look
at the hisory of the Arab-Isreali conflict.

1979 - American Embassy in Iran is stormed by Iranians and embassy
staff taken hostage.

1982 - US Embassy in Beirut is bombed by Muslim extremists.

1982 - US Marine base in Beirut is bombed by Muslim extremists.

1985 - The ship the Achille lauro is seized by Muslim extremists and
one US citizen is killed by them.

1986 - A West German nightclub is bombed, killing an American, by Muslim
extremists based in the Libyan Embassy.

1998 - US Embassies in Kenya and Tanzania bombed by Muslim Extremists.

2000 - US warship USS Cole attacked by Muslim extremists.

The main escalation in this type of terrorist activity can be traced
to the founding of Al-Qaeda by Osama Bin Laden in 1989. Originally formed
to fight a 'jihad' against the Soviet Union in Afghanistan the organisation
soon turned its attention to the United States. Bin Laden issued a fatwa
against the United States because of their involvement in Sudan and
began a campaign of bombings against US bases and forces.

Why did Bin Laden and Al-Qaeda target the United States?

Source - Osama Bin Laden, May 1998

Your position against Muslims in Palestine is despicable and disgraceful.
America has no shame. ... We believe that the worst thieves in the world
today and the worst terrorists are the Americans. Nothing could stop
you except perhaps retaliation in kind.

Source - Osama Bin Laden, May 1998

For over half a century, Muslims in Palestine have been slaughtered
and assaulted and robbed of their honor and of their property. Their
houses have been blasted, their crops destroyed. And the strange thing
is that any act on their part to avenge themselves or to lift the injustice
befalling them causes great agitation in the United Nations which hastens
to call for an emergency meeting only to convict the victim and to censure
the wronged and the tyrannized whose children have been killed and whose
crops have been destroyed and whose farms have been pulverized

Source - Osama Bin Laden, May 1999

If the instigation for jihad against the Jews and the Americans in
order to liberate Al-Aksa Mosque and the Holy Ka'aba Islamic shrines
in the Middle East is considered a crime, then let history be a witness
that I am a criminal.

Source - Osama Bin Laden, October 2001

We swore that America wouldn't live in security until we live it truly
in Palestine . This showed the reality of America, which puts Israel's
interest above its own people's interest. America won't get out of this
crisis until it gets out of the Arabian Peninsula , and until it stops
its support of Israel.

Source: Osama Bin Laden Radio broadcast made following 9/11

"The Palestinian cause has been the main factor that, since my
early childhood, fueled my desire, and that of the 19 freemen (Sept.
11 bombers), to stand by the oppressed, and punish the oppressive Jews
and their allies," the al Qaeda chief said.

"We shall continue the fight, Allah willing, against the Israelis
and their allies, in order to pursue justice for the oppressed, and
we shall not give up one inch of Palestine, as long as there is still
a single true Muslim alive.

Source: Extract from Usama Bin Laden's statement to the hijackers
prior to 9/11

Then every one of you should prepare to carry out his role in a way
that would satisfy God. You should clench your teeth, as the pious early
generations did.

When the confrontation begins, strike like champions who do not want
to go back to this world. Shout, "Allahu Akbar," because this
strikes fear in the hearts of the non-believers. God said: "Strike
above the neck, and strike at all of their extremities." Know that
the gardens of paradise are waiting for you in all their beauty, and
the women of paradise are waiting, calling out, "Come hither, friend
of God." They have dressed in their most beautiful clothing.

If God decrees that any of you are to slaughter, you should dedicate
the slaughter to your fathers and [unclear], because you have obligations
toward them. Do not disagree, and obey. If you slaughter, do not cause
the discomfort of those you are killing, because this is one of the
practices of the prophet, peace be upon him. On one condition: that
you do not become distracted by [unclear] and neglect what is greater,
paying attention to the enemy. That would be treason, and would do more
damage than good. If this happens, the deed at hand is more important
than doing that, because the deed is an obligation, and [the other thing]
is optional. And an obligation has priority over an option.

Do not seek revenge for yourself. Strike for God's sake. One time Ali
bin Abi Talib [a companion and close relative of the prophet Muhammad],
may God bless him, fought with a non-believer. The non-believer spit
on Ali, may God bless him. Ali [unclear] his sword, but did not strike
him. When the battle was over, the companions of the prophet asked him
why he had not smitten the non-believer. He said, "After he spit
at me, I was afraid that I would be striking at him in revenge for myself,
so I lifted my sword." After he renewed his intentions, he went
back and killed the man. This means that before you do anything, make
sure that your soul is prepared to do everything for God only.

Then implement the way of the prophet in taking prisoners. Take prisoners
and kill them. As Almighty God said: "No prophet should have prisoners
until he has soaked the land with blood. You want the bounties of this
world [in exchange for prisoners] and God wants the other world [for
you], and God is all-powerful, all-wise."

Source - Osama Bin Laden, February 2003

This action was done in response for the American political, economical,
and military support to Israel the state of terrorism and to the rest
of the dictator countries in the region.

Source - Osama Bin Laden, February 2003

... the Mujahideen saw the black gang of thugs in the White House hiding
the Truth, and their stupid and foolish leader, who is elected and supported
by his people, denying reality and proclaiming that we (the Mujahideen)
were striking them because we were jealous of them (the Americans),
whereas the reality is that we are striking them because of their evil
and injustice in the whole of the Islamic World, especially in Iraq
and Palestine and their occupation of the Land of the Two Holy Sanctuaries